Ticket 49223 - Fix sds queue locking
    
    Bug Description:  In some cases nspr locks may have allowed a corruption
    in the queue to occur.
    
    Fix Description:  Change to pthread mutex, and fix the naming of
    the struct members.
    
    https://pagure.io/389-ds-base/issue/49223
    
    Author: wibrown
    
    Review by: mreynolds (Thanks!)